My advice, if your handy take it apart and see if the internals got messed up. If you not so mech inclined, have your LBS do it. Either way, the only way to tell what the deal is, is to disassemble it. Sounds like the u-turn is stuck or your not using enough pressure to turn it for fear of breaking your knob again.
Another thought I just had... remove the knob, see if you can turn the nub the cap goes onto with some pliers and see if the adjuster moves. If not a teardown is the only solution. good luck.
FYI, psylos are easy to take apart, especially for your issue. You really only need to loosen the spring assembly, unscrew the bottom bolt @ 1/2 way, tap bolt lightly with a hammer to loosen the spring assembly from the lowers , finish removing the bolt and pull out the spring. Check it's not damaged and see if you can get it to move. Simple. Oh BTW, oil will spill out the bottom of the fork when you loosen the bolt, so watch out.
Good luck.
